National University of Sciences and Technology Technology College of Electrical & Mechanical Engineering Rawalpindi 8. Study the designs of DOHC used in various automobiles. Analyze the designs of intake and exhaust camshafts used in Toyota Corolla twin-cam engine. Use proe software for analysis.
A Project Report De-30
Me (A)
Submitted By: TC Uzair Ali NS Esaam Jamil TC Hassan Warriach Bachelors In Mechanical Engineering Year 2012 Project Supervisor Col. Ikhlaq Khattak Dated: June 14, 2010 1
Acknowledgements:
First of all thank thankss to Allah Allah Almighty Almighty who has given given human human bei bein ngs brill rilliiant ant minds nds and made made us the crown of the of the crea reation. tion. Secondly, condly, we wou would like to honor onor o ur respec respected ted Sir Col. Ikh Ikhlaq Kh Khattak ttak for for his advi advicce and encour ncoura agem gement in maki making this proj proje ect. We W e wou would als also li like to thank thank him him for for always always bein eing available lable for for our guidanc guidance e and hel help insid side and outsid utside the class class.. Finall Finally, y, we wou would li like to thank thank our our paren rents for for their love love.. We We wou would als also like to acknowle acknowledge with apprec ppre ciation tion of their of their suppo support in our our stud studies. ies.
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Abstract:
A camsh camshaf af t tran transslates lates the rotary moti motion on of the engin gine to the rec reciproca iprocati tin ng or oscillati llatin ng moti motion on tha that is used used to opera perate (ope (open n or close) close) the intake ake and exha exhaust valves alves.. It is usuall usually y made made by chill hille ed iron iron casti castin ng and bi billet llet steel. steel. Camsh Camshaf af ts ts can be be classi classif f ied ied into three types name namely OHV, OHV, SOHC and DOHC. Our basi basicc obje objective is to stud study design esigns of t of twin overhe o verhead ad camsh camshaf af ts ts used use d in vario rious automob utomobiiles; es ; design esign and analyze analyze the int ake ake and exha exhaust camsh camshaf af ts ts of Toy Toyota cor corolla twin-cam engin gine usin using pro pro engin gineer sof tware ware.. Therefo here fore, re, we stud studied ied the design esigns of i of intake ake and exha exhaust camsh camshaf af ts ts af ter ter maki making the design esigns in propro-e e. Furthermo Furthermore, re, we have done done stress analysis analysis to get into the depth of the very topic pic whi whicch conclu concludes our proj proje ect repo report. rt.
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Table of Contents:
Acknowledgements
Abstract Table of Contents
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List of figures
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1. I ntroduction ntroduction 2. Material and manufacturing of camshaft 2.1. Chilled iron casting 2.2. Billet steel 3. Types of camshafts 3.1. OHV or push rod 3.1.1. Merits 3.1.2. Demerits 3.2. SOHC 3.2.1. Merits 3.2.2. Demerits 3.3. DOHC or twin OHC 3.3.1. Merits 3.3.2. Demerits 4. History of DOHC 5. Design of DOHC used in various automobiles 6. Engine specifications of Toyota corolla used
6 6
7 7
7
9
10 11 12
7. Designs of intake camshaft of Toyota Corolla twin-cam engine using pro-e 13 8. Designs of exhaust camshaft of Toyota Corolla twin-cam engine using pro-e 15 9. Study of designs of intake and exhaust camshafts 16 10. Stress analysis of exhaust camshaft of Toyota Corol la twincam engine using pro-e 18 11. Stress analysis of intake camshaft of Toyota Corolla twincam engine using pro-e 19 12. Conclusions from the stress analysis of intake and e xhaust camshafts of Toyota corolla twin-cam twin -cam engine 20 ibliography 22 13. B ibliography
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Table of Figures:
F ig ig 3.1a:
4-cylinder 8 valves OHV engine
F ig ig 3.2a:
4-cylinder 8 valves SOHC engine
F ig ig 3.2b:
SOHC
F ig ig
3.3a : 4-cylinder 16 valves DOHC engine
F ig ig 3.3b:
DOHC
F ig ig
5a: Harley Davidson bike (left) and its DOHC design (right)
F ig ig
5a: Harley Davidson bike (left) and its DOHC design (right)
F ig ig
5c: Toyota Corolla (left) and its DOHC design (right)
6a: Toyota Corolla (right) of above specifications F ig ig 7a: Intake camshaft ( 3D view) F ig ig
F ig ig
7b: Cam lobe and holes for lubrication of intake camshaft
7c: Gear attached to intake camshaft ( 3D view) F ig ig 7d: Side view of intake camshaft F ig ig 8a: 3D view of exhaust camshaft F ig ig
F ig ig
8b: Cam lobe and holes for lubrication of exhaust camshaft
F ig ig
8c: Side view of exhaust camshaft
F ig ig
9a: A typical cam and its distinct regions
F ig ig
10a: Stress on exhaust camshaft
F ig ig
10b: Displacement on exhaust camshaft
F ig ig
10c: P-level on exhaust camshaft
F ig ig
11a: Stress on intake camshaft
F ig ig
11b: Displacement on intake camshaft
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1. Introduction:
A camsh camshaf af t tran transslates lates the rotary moti motion on of the of the engin gine to the rec reciproca iprocati tin ng or oscillati llatin ng moti motion on tha that is used used to opera perate (ope (open n or close) close) the intake ake and exha exhaust valves alves.. It has cam lobes lobes on the shaf shaf t. The camsh camshaf af ts ts are driven riven f rom the cranksh ankshaf af t by camsh camshaf af t drivers whic hich may may be gea gear, belt or chain. The camsh camshaf af t pushes the valves alves.. The valves alves pushed pushed back by by the reac reactive tive for force of the valve alve sprin spring .
2. Material and manufacturing of camshaft:
2.1 Chilled iron casting:
This is a good ch choice for for high volu olume prod produ uction. tion. A chi chill lle ed iron iron camsh camshaf af t has a resistanc resistance e against wear because cause the camsh camshaf af t lobes lobes have been een chill hi lle ed , whic hich makes makes them them harder. er. When hen maki making chill hille ed iron iron casti ca stin ngs, other elements are adde added to the iron iron be before fore casti castin ng to make make the materi material al more more suitabl suitable e for for its appl pplicati cation. on. 2.2
Billet Steel:
When hen a high quality ality camsh camshaf af t is req required uired, engin gine build uilders ers and camsh camshaf af t manu manufacturers facturers choose oose to make make the camsh camshaf af t f rom steel steel billet llet.. This method ethod is als also used used for for low volu olume prod produ uction. tion. This This is a much more more tim time consu consum ming proc process, ess, and is gen generall erally y more more expen expe nsive than than other method ethodss. However However the f inished ished prod produ uct is far far superio superi or. When hen maki making the camsh camshaf af t, t, CNC lathes, lathes, CNC mi milli llin g machi machin nes and CNC camsh camshaf af t grind grinders ers will be used. used. Diff eren erent types of steel steel bar bar can be be used. used. One One exam examp ple is EN40b. Whe W hen n manu manufacturi facturin ng a camsh camshaf af t f rom EN40b, the camsh camsh af t will als also be b e hea heat trea treated. ted. T he method ethod of he of hea at trea treatment is gas nitrid itriding, whic hich changes anges the micro-stru o-struccture of the of the materi material. al. It It gives a surfac surface e hardness dness of 5560 on the HRC. These These types of camsh camshaf af ts ts can be be used used in high perfo perforrmance mance engin gines. es.
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3. Typ
3.1
of Camshaft C amshaft::
Push Pu sh od o OHV: In ove head valve engine design, the the camsh amshaf t is installed inside the the
engine bloc
and valves a e ope ope ated through lif ters, pus pushrods hrods and roc roc er
arms.
Fig 3.1a: 4-cyl -c ylinder der 8 valves OHV OHV engine 3.1.1
M its: An
OHV OHV engine is ver very simple and it has has more ore compact size and is prove proven
to be be dura urable. 3.1.2
D m
its:
It is diff icult to pre precisely control trol the the valve timing at high rpm rpm due to
higher inertia caused by lar larger amou amount of of valve valve tra train components (lif ter pus pushrod hrod-roc roc er arm . Also lso it is ver very diff icult to install more ore tha than two valves per cylinder der or implement some lat latest es t te technologies such as Variable Valve Timing
3.2
OHC o OHC:
In the the SOHC engine, the the camsh amshaf t is installed in the the cylinder der head and inlet let
and e haust valves are ope operated eithe ther by the the roc roc er arms or directly throug h the the lif ters.
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Fig 3.2a: 4-cyl -cylinder der 8 valves SOHC engine
Fig 3.2b .2b: SOHC 3.2.1
M
its:
Valves are ope operated almo almost directly by the the camsh amshaf t - easy to achieve the the perfec fect timing at high rpm. rpm. It is poss possible to install three three or f our our valves per cylinder der. The The SOHC design has less reciproc procating mass tha than a comparable pus pushrod hrod design. This allow allowss f or or higher engine speeds, which in turn will increase powe power output f or or a given torque. torque. 3.2.2
D m
its:
8
An
OHC engine requires a timing belt elt or chain with relat elated components -
more ore comple and more ore e pensive design.
3.3
DOHC o Twin OHC:
It use two camsh amshaf ts, the the inlet let camsh amshaf t drives the the inlet let valves while the the
e haust drives e haust valves through the the valve lif ters. The The Cam lobe obe makes contact with the the head of the the valve lif ter directly or via a thin round plat late (pad (pador or shim which is pos positioned on the the valve lif ter head. head.
Fig 3. 3a: 4-cyl -cylinder der 16 valves DOHC engine It is poss possible to install multiple valves per cylinder der and plac lace intake
valves on the the oppos opposite side f rom rom e haust vales. The The main reaso eason to use use double ouble overh verhead ead cams is to allow allow f or or more ore intake and e haust valves. More More valves mean tha that intake and e haust gases can flow flow more ore f reely because the there are more ore ope openings f or or them them to flow flow through. This increases the the powe power of the the engine. Thus Thus, it can prod produce more ore horse horse powe powers with smaller smaller engine volume. For inder comparison: The The 3.5-liter V6 DOHC engine of 2003 Nissan Pathf thf in der has 240
hp, similar lar to 245 hp of of th the e 5.9 -liter V8 OHV OHV engine of 2 f 2003 Do Dod dge Dura Durango.
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Fig 3.3b: DOHC
3.3.1
erits:
It is most most widely used used in cars cars now-a-days now-a-da ys.. It has high eff icienc iency y. It possibl ssible e to install stall mu m ultipl tiple valves alves per cylinder nder and it can adopt adopt variabl riable e tim timing.
3.3.2
e erits:
More More comp complex and more more expen expensive design. esign.
4. History of DOHC:
Among Among the early pion pioneers eers of DOHC were were I sotta tta Fra Fraschin hini's Giustino iustino Catt Cattan ane eo, Austro-Da ustro-Daiimler's mler's Ferd Ferdinand Pors Porscche Stephen tephen Tomcz Tomczak (in the Prinz Heinrich), Heinrich ), and W. O. Be Bentley (in 1 919). Sunbe nbeam buil uilt small nu numbers mbers betw et ween een 1921 and 1 923. The f irst irst DOHC engin gines were either two- or or four four--valve alve per cylinder nder raci acing car car design esigns f rom comp companies anies like Fia Fiat (1912), Peugeo eugeot Grand Prix Prix (1913, 4 valve), alve), Alfa Rome Romeo Grand Prix Prix (1914, 4 valve) alve) and 6C (1928), Maser Masera ati Tipo ipo 26 (1926), Buga ugatti Type 51 (1 931). 10
Whe When DOHC te technology was introd troduced in mainstream tream veh vehicles, it was commo mmon f or or it to be be heavily advert advertised. While used at f irst in limited prod production and sports ports cars, Alfa Ro Rome meo o is one of the the twin cam s great eatest es t proponents, 6C Sport the the f irst Alfa Ro Rome meo o road road car using DOHC engine was introd troduced in 1928, ever ever since this has been tradema trademarrk of all Alfa Ro Rome meo o engines. Fiat was one of the the f irst car companies to use a belt elt-driven DOHC engines across ross the their complet lete prod product line, in the the mid -1960s., Jaguar's r's XK6 DOHC engine was displayed in the the Jaguar XK1 XK120 at the the Lo ndon Motor Show in 1948 and used across ross the the entire Jaguar range through the the lat late 1940s, 1950 and 1960s. By the the lat late 1970s, Toy Toyota ota was the the best est seller seller of of DOHC DOHC engines.
5. D
si
s of D
C used
i
vari ous automobiles:
Fig 5a: Harley Davidso dson bike (lef t) t) and its DOHC design (right)
Fig 5b: Mitsubishi Galant (lef (lef t) t) and its DOHC design (right)
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Fig 5c: Toy Toyota ota Corolla Corolla (lef t) t) and its DOHC design (right)
6. Engi Engine specif ic ic at ions of Toyota Corolla used:
Mod l: 2006 En in : 1. 8 liter f our our cylinder ders, double ouble overh verhead ead cam, f our our valves per cylinder der Ho s power: 126 @ 6,000 rpm rpm Torque: 122 lb.-f t. @ 4,200 rpm rpm Transmission: 5- speed manual
Fig 6a: Toy Toyota ota Corolla Corolla (right) of of above bove specif ications
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7. Designs of intake camshaft of Toyota Corolla twincam engine, using Pro-e:
Intake ake camsh camshaf af t (3D view Fig 7a: Int view)
Fig 7b: Cam lobe lobe and holes oles for for lubrica ricati tion on of i of intake ake camsh camshaf af t 13
Fig 7c: Ge Gear attac ttache hed d to i ntake ake camsh camshaf af t (3D view view)
Fig 7d: Si Side view view of i of i ntake ake camsh camshaf af t
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8.
Designs of exhaust camshaft of Toyota Corolla twin-cam engine, using Pro-e:
Fig 8a: 3D view view of exh of exha aust camsh camshaf af t
Fig 8b: Cam lobe lobe and holes oles for for lubrica ricati tion on of exh of exha aust camsh cam shaf af t 15
Fig 8c: Si Side view view of exh of exha aust camsh camshaf af t
9. Study of designs of intake and exhaust camshafts: The camsh camshaf af ts ts f uncti nction on in an engin gine is to open pen and close close the valves alves.. Its design esign resul results in valves alves bein eing open pened and close clo sed d at a t contr controll olle ed rate of spee of speed d as as well as at a prec precise tim time in rela relati tion on to piston piston position. sition. DOHC have four four lobes lobes per cylinder, nder, two to drive d rive the intake ake valve alve and two to drive d rive the exha exhaust valve alve.. Camsh Camshaf af t ha s a shaf shaf t, t, cam lobes lobes on it and the bearin ring jour journal nalss. The cam lobes lobes convert convert the rotator moti motion on of the camsh camshaf af t to the rec reciproca iprocati tin ng moti motion on of the of the valve alve tra train and valves alves.. The T he design esign of the cam lobe lobe cont contour has a major major eff ect on the engin gine perfo perforrmance mance. The amou amount of valve alve open pening, how long long the valve alve rema remaiins open pen, when hen the valves alves open pen and close clo se and the speed speed at whic hich valves alves open pen and close clo se are all deter determ mined by the cam lobe lobe design. esign.
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Fig 9a: A typical typical cam and its distinc istinctt region regionss The camsh camshaf af t rotates in a clock wise w ise direc irection. ti on. Four region regionss are identif tif ied ied sta startin rting f rom the bott bottom om in a cou counter cloc cloc k wise wise direc irection: tion: base base circl ircle, e, open pening ramp, amp, nose, nose, and closi closin ng ramp amp. Each Each region region is identif tif ied ied by degree locati location ons, s, sta startin rting at
0
degree at the nose, nose,
60
at the closi closin ng ramp, amp, 180
at the base base circl ircle e and 300 at the open pening ramp amp. Camsh Camshaf af t lobe lobe wear is cause caused d by f ric riction tion bet b etw ween een the cam lobe lobe and the cam follower follower.. Insu Insuff ff icien ient, exc excessive valve alve sprin spring ten tension sion,, exc excessive valve alve lash lash , hyd hydraulic lif ter ter fai failure and dirty dirty oil will contri contrib bute to early and rapid pid wear. Wor Worn cam lobes lobes reta alve tim ower and retard valve timing whic hich is detrim etriment al to engin gine power perfo perforrmance mance. To av a void suc such damage, damage, there are holes oles on the camsh camshaf af t whic hich pro provid vide way way to oi oil for for lubrica ricati tion. on.
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10.
Stress analysis of exhaust camshaft of Toyota Corolla twin-cam engine, using Pro-e:
Fig 10a: Stress Stress on exha exhaust camsh camshaf af t
Fig 10b: Disp Displac lace ement on exha exhaust camsh camshaf af t
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Fig 10c: P-leve P-levell on exha exhaust camsh camshaf af t
11.
Stress analysis of intake camshaft of Toyota Corolla twin-cam engine, using Pro-e:
Fig 11a: Stress Stress on intake ake camsh camshaf af t 19
Fig 11b: Disp Displac lace ement on intake ake camsh camshaf af t
12. Conclusions from the stress analysis of intake and exhaust camshafts of Toyota corolla twin-cam engine:
If we observe observe the wor working of camsh camshaf af ts, ts, we see tha that only only one one pair of the lobe pair touch the valve alve pair (intake ake or exha one tim rotatin ting cam lobe exhaust) at one time whil hile the rema remaiining are orien riented ted at at diff eren erent ang angles . The The ends nds of the of the cam lobes lobes force on the valve alve to move move downwar downward causi ca usin ng it to open. exert for pen. Due to this acti action on there is equal and opp oppo osite reac reacti tion on by by the valve alve sprin spring. Now to do analysis analysis we have consi consid dered ered o ne end (the ( the shaf shaf t in be b earin ring sid side) to be f ixed ixed and the other end ( the shaf shaf t attac ttache hed d to the gea gear and gea gear to the tim timing chain) to be be f ree. ree. We als also have consi consid dered ered tha that the for forces are acti actin ng on lobe pair nearest to the gea the cam lobe gear. Accor According to the analysis, analysis, the camsh camshaf af t acts acts as a canti cantillever. ever. Stresses are more more near the bearin ring sid side. The The analysis analysis als also show showss tha that stresses are maxi maxim mum around the holes oles due to stress conce concentra tration. tion. Als Also the stress is more more at the region region where where the shaf shaf t cha nges diameter ameter..
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We als also see tha that the displac isplace ement is maxi maxim mum near the gea gear end whic hich grad gradu ually ally decrea reases as we move move away away f rom it. it. The p level evel diagram gram show showss the poten tential tial level. evel. It has maxi maxim mum values alues betw etween een the pair of cam lobe lobe (whi (whicch are appl pplyin ying for forces on the valves alves at the very instan stant) t).. The bar bar at the top right of the stress analysis analysis window show showss diff eren erent values alues f rom mi minimum (deep (deep blue) blue) to maxi maxim mum (re (red d).
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13.
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